Pipe and conduit laying devices are known including U.S. Pat. No. 4,289,424 to Shefbuch and Rue, issued Sep. 15, 1981 and titled Apparatus for Laying Conduit, Cable, and the Like in or Beneath Fill Material; U.S. Pat. No. 5,174,685 to Buchanan issued Mar. 18, 1992 and titled Flexible pipe laying and covering apparatus; U.S. Pat. No. 6,120,209 to Evans issued Sep. 19, 2000 and titled Method of Installing Drainfield Pipe; U.S. Pat. No. 6,336,770 to Evans issued Jan. 8, 2002 and titled Drainfield Pipe Installation Device; U.S. Pat. No. 7,632,408 to Everson issued Dec. 15, 2009 and titled Passive Drain Field System For Drainwater Treatment and Associated Methods; U.S. Pat. No. 4,268,189 to Good issued May 19, 1981 and titled Apparatus and Method for Supporting and Positioning Pipe During the Construction of Drain Fields and the Like; U.S. Pat. No. 5,437,424 to Netz, Sr. Issued Aug. 1, 1995 and titled Septic Pipe Field Drain Holders; U.S. Pat. No. 5,871,306 to Tilcox issued Feb. 16, 1999 and titled Pipe Supporting Apparatus; U.S. Pat. No. 5,042,958 to Stenersen issued Aug. 27, 1991 and titled Method and Apparatus for Installing Sewer and Drainage Pipe.
Use and Need—Leach Line Extrusion Process. Leach lines are used in on-site septic systems to introduce septic tank effluent into the soil for absorption and further treatment in the soil. The most common type of leach line is constructed of a trench partially filled with rock as an aggregate with perforated pipe inside the rock for the distribution of effluent. The aggregate type is not limited to rock. Other types of aggregate include, but are not limited to: tire chips, crushed glass, plastic beads, or polystyrene beads. The perforated pipe in the leach line is connected to the header pipe system which controls the distribution of effluent in the septic system.
The construction of a conventional aggregate/pipe leach line is constructed by excavating a trench on a specific grade, level or slightly sloped according to local regulatory jurisdiction. The aggregate rock that is to be below the perforated pipe is then placed to a specific depth. The perforated pipe is placed on the rock then a second layer of rock is placed to a depth just covering the pipe. Geotextile filter fabric or paper is rolled over the top of rock to protect the leach line from soil intrusion.
The conventional style of leach line construction is labor intensive as a machine must pour rock blind into the trench to a specific depth which is very hard to control. There is a lot of shovel work fine grading the rock to the desired depth within required tolerances. Perforated pipe must be laid and glued together then manually held in place or weighted to prevent movement as the upper layer of rock is placed. After the upper layer is again placed blind by machine, more shovel work is required to fine grade the top of the leach line to meet required tolerances.
There exists a style of corrugated, flexible, perforated pipe commonly constructed of HDPE plastic that is less expensive than the other types of rigid perforated pipe. This pipe conforms to the ASTM F405 standard. This pipe though, is nearly impossible to install in a leach line trench using conventional methods as it is too flexible to stay put, once placed. There is a large cost advantage to using this pipe in leach line trenches if a successful method can be created. The flexible style F405 HDPE pipe is commonly shipped in rolls. This pipe can be installed in a continuous fashion eliminating the need to glue joints. This pipe can also be installed in contoured trenches without the need to install elbow joints in the pipe.
There are designs in the existing art including pipe holders, both reusable and disposable, that hold the pipe at the required elevation in the trench before aggregate filling. These designs require that a rigid pipe is used in the trench in order to resist the forces of the aggregate as it falls into the trench. Pipe holders are either lost in the trench or are required to be retrieved out of the rock in order to be reused. With these pipe holders, there remains the requirement to fine grade the top of the leach line aggregate by hand before placing filter fabric by hand.
I propose a new method of construction of conventional style leach lines. A process of extrusion of the leach line itself would answer a lot of the problems associated with its construction. A short trench segment would be excavated to grade by conventional means such as with a backhoe or excavator. A device loaded with all the required materials could be used to extrude the leach line horizontally along the trench bottom with the pipe in place, perfectly to grade, with fabric placed on top of the aggregate. The device would be advanced along the trench by the excavation equipment just behind the excavation as it is performed. This would be accomplished in one pass with far less manual labor than the conventional method.
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